Unexpected complete remission after recurrence in pancreatic cancer: a case report on comprehensive multimodal therapy.

Pancreatic ductal adenocarcinoma (PDAC) is among the most aggressive malignancies of the digestive tract, with a 5-year survival rate below 13%. It often infiltrates surrounding tissues early, making it challenging to distinguish primary pancreatic involvement from adjacent malignancies on imaging. Despite advancements in surgery, chemotherapy, and radiotherapy, PDAC still carries a high risk of recurrence. Here, we present a case initially diagnosed by imaging and biopsy as a duodenal malignancy. The patient underwent robotic-assisted laparoscopic pancreaticoduodenectomy, and final pathology confirmed moderately differentiated PDAC. Postoperative treatment with eight cycles of a modified AG (GN) regimen achieved 17 months of tumor-free survival. Following the detection of peritoneal metastases, the patient received six months of NALIRIFOX therapy and achieved complete remission by the ninth month after recurrence. This case underscores the critical role of surgery and adjuvant chemotherapy in resectable PDAC. It also highlights the importance of vigilant postoperative surveillance for early detection of recurrence and emphasizes the concept of pseudoprogression when interpreting imaging findings.